The present invention generally relates to an optical fiber quadrant detector and, in particular, relates to one such optical fiber quadrant detector having a sensing head wherein each quadrant includes a plurality of light transmitting optical fibers and a plurality of light receiving optical fibers.
Quadrant detectors are generally known in the art. Full quadrant detectors are frequently used to optically align a workpiece to a preselected position. For example, in setting up a mechanism, such as an optical bench, the bed of the mechanism can be aligned parallel with a reference plane by use of a precisely positioned quadrant detector disposed in the reference plane but removed from the bed of the mechanism. In such an operation a mirror could be affixed to the bed of the mechanism and, by measuring the relative tilt in the x and y directions with the quadrant detector, the bed can be precisely positioned with respect to the reference plane of the quadrant detector. In such an operation the quadrant detector is, effectively, operated as a null detector, i.e. the goal is to align the reflected light from the bed until each quadrant receives the same amount of reflected light.
Another use for quadrant detectors is the measurement of optical properties, such as astigmatism, of spherical lenses. In such an application a lens to be measured is disposed so that the light reflected therefrom is directed onto the quadrant detector. The amount of light reflected from the lens is then determined as the lens is rotated. The variation of the light measured in each quadrant gives a measure of the aberration of the lens.
In general, in most quadrant detector arrangements the apparatus used frequently includes beam splitting optics as well as various lenses. One significant drawback associated with the use of beam spitters is that only about one half of the original light signal is ultimately projected toward the workpiece. Hence, such arrangements generally require powerful light sources and/or relatively sensitive quadrant detector devices.
Currently, conventional quadrant detector devices include a light sensitive surface adapted to produce an electrical signal having a known relationship to the intensity of the light impinging on the surface. To fully utilize such devices requires that each quadrant react identically, or at least be calibrated so that the output signal of each quadrant is the same as each other quadrant for the same light intensity. A further difficulty with such detectors is that the electrical response of the material making up the light sensitive surface may vary over time and operating conditions. Hence, such quadrant detectors must be frequently recalibrated to compensate for such variations. These drawbacks tend to limit the usefulness and applications for quadrant detectors.
Consequently, it is highly desirable to provide a quadrant detector that substantially completely overcomes the above-recited drawbacks of conventional quadrant detectors.